Fuel injection system for internal combustion engines having controlled exhaust gas recycling

Abstract

What follows is a description of various exemplary embodiments of a fuel injection system for an internal combustion engine with exhaust gas recycling controlled by a throttle valve situated in the suction tube of the system. The throttle valve is in turn controlled by a servomotor having a displaceable piston connected to the throttle valve. The piston is displaceable against a variable restoring force exerted against it and produces displacements of the throttle valve between two positions, one corresponding to a fully opened position of the throttle valve and closed exhaust gas recycling line, and the other corresponding to a substantially closed throttle valve.

What is claimed is: 
     
       1. A fuel injection system for an internal combustion engine, comprising in combination: (a) a suction tube through which an air flow is established;   (b) an exhaust gas line through which an exhaust gas flow is established;   (c) an exhaust gas recycling line connected to the exhaust gas line and to the suction tube, the suction tube connection defining therein a discharge outlet of the recycling line;   (d) a throttle valve controlling the flow of the exhaust gas in the recycling line, said throttle valve being mounted within the suction tube upstream of and in operative association with the discharge outlet of the recycling line;   (e) air metering means mounted to partially extend into said suction tube and be displaceable by the air flow thereon;   (f) fuel injection means including means for arbitrarily varying the fuel quantity delivered by the fuel injection means;   (g) a servomotor including a displaceably mounted piston, a working chamber and means connecting the piston to the throttle valve for controlling the opening thereof;   (h) means providing a variable restoring force against the displacements of the servomotor piston;   (i) a differential pressure valve having an uncontrolled pressure chamber, a controlled outflow opening in a chamber having an essentially constant reference pressure, and means connecting the controlled outflow opening to the working chamber of the servomotor;   (j) fuel metering means including a control slide connected to and displaceable by the air metering means, a throttle whose cross-section is varied by the displacements of the control slide, and means for establishing a regulatable, substantially constant return force acting against the displacements of the control slide; and   (k) a fuel suction line connected to the fuel injection means, the uncontrolled pressure chamber of the differential pressure valve and, upstream of its connection to the uncontrolled pressure chamber, to the throttle whose cross-section is varied, wherein: (i) the arbitrarily varied fuel quantity serves as a reference parameter for the operation of the servomotor; and   (ii) the servomotor piston is displaceable, against the variable restoring force, between two positions, one corresponding to a fully opened position of the throttle valve and closed exhaust gas recycling line, and the other corresponding to a substantially closed throttle valve.     
     
     
       2. The fuel injection system as defined in claim 1, further comprising an adjustable stop, wherein, the substantially closed position of the throttle valve can be determined by the adjustable stop. 
     
     
       3. The fuel injection system as defined in claim 1, wherein the throttle valve includes a recess as a minimum throughput cross-section. 
     
     
       4. The fuel injection system as defined in claim 1, wherein a spring arrangement comprising at least one spring having a defined force characteristic serves as the restoring force means. 
     
     
       5. The fuel injection system as defined in claim 1, wherein an adjustable constant hydraulic force constitutes the restoring force. 
     
     
       6. The fuel injection system as defined in claim 1, further comprising: (l) a fuel supply line exposed to differential pressure;   (m) an engine temperature sensor;   (n) a solenoid valve connected to the sensor;   (o) a connecting line connected between the means connecting the controlled outflow opening to the working chamber of the servomotor and the fuel supply line, wherein the solenoid valve closes, via the connecting line, the means connecting the controlled outflow opening to the working chamber of the servomotor and the fuel supply line upon the sensor sensing a given temperature limit.   
     
     
       7. The fuel injection system as defined in claim 1, wherein the fuel injection means includes a working cylinder defining a working chamber, a fuel quantity adjustment member and a spring, wherein the servomotor piston defines a control edge, and wherein the fuel injection system further comprises: (l) throttle means connected to the servomotor for communicating with the working chamber of the servomotor, said throttle means being controlled by the control edge of the servomotor;   (m) means connecting the throttle means to the working chamber defined by the working cylinder; and   (n) further throttle means connected to said means defined in (m) above, said further throttle means having a smaller cross-section than said throttle means and serving to relieve the working chamber defined by said working cylinder, said working cylinder serving to produce a restoring action on the fuel quantity adjustment member in opposition to the force exerted by said spring.   
     
     
       8. The fuel injection system as defined in claim 7, further comprising: (o) a fuel supply line exposed to a reference pressure;   (p) a solenoid valve;   (q) a connecting line connected between the means connecting the controlled outflow opening to the working chamber of the servomotor and the fuel supply line, wherein the solenoid valve arbitrarily closes, via the connecting line, the means connecting the controlled outflow opening to the working chamber of the servomotor and the fuel supply line.   
     
     
       9. The fuel injection system as defined in claim 1, further comprising a fuel supply pump and a pressure control valve, wherein a reference pressure is established which comprises the delivery pressure of the fuel supply pump, or wherein said delivery pressure is regulatable by the pressure control valve. 
     
     
       10. The fuel injection system as defined in claim 9, wherein the restoring pressure and the reference pressure are equal and are regulatable by the pressure control valve. 
     
     
       11. The fuel injection system as defined in claim 9, further comprising a pressure reducing valve disposed in the fuel suction line between the differential pressure valve and the fuel injection means. 
     
     
       12. The fuel injection system as defined in claim 11, wherein the suction tube includes a conical portion, and wherein the air metering means includes a low friction pivot arm and a pivotable baffle plate mounted on the pivot arm in the conical portion of the suction tube. 
     
     
       13. The fuel injection system as defined in claim 1, further comprising a fine steel wool soot filter insert in the exhaust pipe, wherein the exhaust gas recycling line branches off downstream of said filter. 
     
     
       14. The fuel injection system as defined in claim 1, wherein the fuel injection means includes an injection pump and a heat exchanger in a short circuit line, via which the fuel quantity flowing to the injection pump can be recycled to the suction side input of the injection pump. 
     
     
       15. The fuel injection system as defined in claim 1, further comprising a gas pump disposed in the suction tube adjacent to the discharge of the exhaust gas recycling line. 
     
     
       16. The fuel injection system as defined in claim 1, further comprising a cooling device disposed in the suction tube adjacent to the discharge point of the exhaust gas recycling line.